基于高温气体效应的磁流体流动控制研究进展

高超声速飞行器强激波后高温气体形成具有导电性的等离子体流场,电离气体为磁场应用提供了直接工作环境.磁流体控制技术利用外加磁场影响激波后的离子或电子运动规律,可有效地改善高超声速飞行器气动特性,在飞行器气动力操控和热环境管理等方面均具有广阔的应用前景; 同时,超导材料及电磁技术的发展又重新推动了这一领域的研究热潮.虽然国内外在高超声速磁流体流动控制领域已开展了一些研究工作,但其实验研究依然极具挑战, 且由于实验条件及测量技术等限制,其压力、热流等参数的测量并没有得出较为系统的结论,因此需要对影响脱体激波距离、热流、压力变化的规律及机理进行深入研究; 同时,数值模拟方法和理论分析也亟待可靠的实验数据来对其进行验证.本综述调研和讨论了基于高温真实气体效应的磁流体流动控制技术研究,主要针对磁流体流动控制的试验技术、数值模拟、理论方法以及流动控制的主要研究方向等进行了总结,并对其发展趋势进行了讨论和展望.      

长试验时间爆轰驱动激波风洞技术研究

地面试验是先进高超声速飞行器研制的主要手段之一,获得满足高超声速气动实验研究的长时间高焓气流是发展激波风洞技术的关键难题之一.依据反向爆轰驱动方法,针对满足超燃试验有效时间的要求,讨论了爆轰驱动激波风洞运行缝合条件匹配、喷管起动激波干扰控制和激波管末端激波边界层相互作用等因素对激波风洞试验时间的制约及其相应的解决方法.应用这些延长试验时间的激波风洞创新技术,成功研制了基于反向爆轰驱动方法的超大型激波风洞,试验时间长达100ms,并有复现高超声速飞行条件的流动模拟能力.      

磁流体动力学斜激波控制数值模拟分析

高超声速飞行器MHD(磁流体动力学)斜激波控制应用的关键在于理解等离子体斜激波流场与磁场的相互作用规律,这里发展了全MHD数值模拟方法对其进行研究,数值方法基于八波方程附加源项形式,进行有限体积离散,采用了Roe求解器、OC-TVD空间格式和LU-SGS方法,且采用投影方法降低磁场伪散度误差.考察外加均匀磁场的马赫10无粘导电拐角流动,压缩角为10°.结果中散度误差较低,并且通过激波参数验证了结果的准确性.流场显示,磁场使得激波角增大,部分情况下出现了快、慢激波结构,其中快激波变化更明显;壁面压强根据磁场的不同出现了不同程度的降低.最后采用群速度图方法进行了快慢激波形式分析,解释了磁场影响下流场形式变化机理.     

触摸高温气体动力学

回顾了高温气体动力学与高超声速科技相关的一些重要研究进展,探讨几个具有基础性研究意义的方向：即高超声速流动模拟;高温气体热化学反应机制;高超声速流动滞止区预测;高超声速边界层转捩和激波/激波相互作用诱导的气动热问题．这些研究方向与高温气体效应和强激波密切相关,对高超声速科技关键技术的突破起着重要作用．     

面向控制研究的高超声速飞行器气动力与动力一体的建模新方法

高超声速飞行器采用乘波构形后,将对其模型研究带来新挑战,主要体现在建模过程中应充分考虑气动、推进与控制作用相互耦合,因此为了保证建模的准确性,有必要引入新方法来研究高超声速飞行器的模型.本文基于高超声速空气动力学理论,提出了一种高超声速飞行器纵向模型研究的新方法,该方法采用斜激波理论、普朗特-迈耶关系式及瑞利流原理来估...     

多体空气动力学研究进展

多体飞行器普遍存在于航空航天、空天和武器领域中, 主要有以下三大类型: (1) 多个飞行器相互不接触的近距离飞行; (2) 多体飞行器相互接触或组合飞行; (3) 多体飞行器回收或解锁分离过程的相对运动. 多体飞行器在飞行、回收或分离过程中存在相互的流场干扰或作用, 使多体飞行器具有不同于孤立体飞行器的流动物理或特征, 特别是在超声速、高超声速的多体流动中, 多体间存在多重激波反射、衍射以及激波与旋涡、激波与边界层相互干扰或作用, 这些复杂流动能显著地改变多体飞行器的空气动力学特性. 作者引入“多体空气动力学”概念对多体飞行器这一类问题进行概括和总结, 并阐述其基本内涵、应用场景和研究方法/手段及典型多体构型的超声速/高超声速流动结构和特征.      

火星科学实验室气动特性数值分析

针对火星着陆探测器进入-下降-着陆过程的高超声速进入阶段,求解三维流体动力学Navier-Stokes 方程与化学反应动力学模型,分析火星科学实验室进入火星大气时的化学非平衡效应、探测器周围的流场结构和气动特性在化学非平衡效应影响下的变化. 结果表明,CO₂ 在激波后大量分解,消耗大量能量;在化学非平衡效应影响下,探测器头部激波脱体距离大幅减小,尾迹旋涡运动减弱;化学非平衡效应影响下探测器升力系数变化不大,阻力系数高于完全气体,升阻比略低,配平攻角小于完全气体.     

高超声速飞行复现风洞理论与方法

针对高超声速飞行伴随的热化学反应流动,本文回顾了郭永怀先生的科研理念和学科布局,综述了他亲手成立的高温气动团队在高超声速飞行风洞实验模拟理论与方法方面的研究进展.高温气体的迅速产生与迅速应用是一种理想的风洞运行方法,而激波管就是这样一种实验装备.论文首先介绍了激波管技术的基本理论与方程,指出将其用于高超声速流动实验模拟时所具有的独特优势.然后讨论了应用激波风洞复现需要的高超声速飞行状态的可行性、基本方程和需要解决的关键问题.针对这些关键问题,进一步介绍了如何应用爆轰现象研发激波风洞驱动技术的理论,并给出了基于爆轰驱动方法的技术发展和工程应用验证.最后,论文介绍了爆轰驱动激波风洞的界面匹配条件,该条件奠定了长实验时间激波风洞运行基础,是其他驱动方法尝试解决而没能完全解决的难题.高温气动团队关于高超声速飞行复现风洞的理论与技术研究,实现了郭永怀先生的战略规划,成就了国际领先的高超声速热化学反应流动研究平台.      

高超声速飞行复现风洞理论与方法

针对高超声速飞行伴随的热化学反应流动,本文回顾了郭永怀先生的科研理念和学科布局,综述了他亲手成立的高温气动团队在高超声速飞行风洞实验模拟理论与方法方面的研究进展.高温气体的迅速产生与迅速应用是一种理想的风洞运行方法,而激波管就是这样一种实验装备.论文首先介绍了激波管技术的基本理论与方程,指出将其用于高超声速流动实验模拟时所具有的独特优势.然后讨论了应用激波风洞复现需要的高超声速飞行状态的可行性、基本方程和需要解决的关键问题.针对这些关键问题,进一步介绍了如何应用爆轰现象研发激波风洞驱动技术的理论,并给出了基于爆轰驱动方法的技术发展和工程应用验证.最后,论文介绍了爆轰驱动激波风洞的界面匹配条件,该条件奠定了长实验时间激波风洞运行基础,是其他驱动方法尝试解决而没能完全解决的难题.高温气动团队关于高超声速飞行复现风洞的理论与技术研究,实现了郭永怀先生的战略规划,成就了国际领先的高超声速热化学反应流动研究平台.     

高焓湍流边界层壁面摩阻产生机制分析

高超飞行器在中低空以极高马赫数飞行时,飞行器表面会遇到湍流与高温非平衡效应耦合作用的新问题.这种高焓湍流边界层壁面摩阻产生机制是新型高超声速飞行器所关注的基础科学问题,厘清此产生机制可以为减阻方法的设计提供指导,具有重要的工程实用价值.本文选取高超声速飞行时楔形体头部斜激波后的高焓流动状态,开展了考虑高温非平衡效应的湍...     

Hypersonic flow past a plane magnetic dipole with parallel orientation of the magnetic moment and free-stream velocity vectors for moderate magnetic Reynolds numbers

The two-dimensional problem of hypersonic flow past a cylindrical body with a plane magnetic dipole in the presence of an external magnetic field is considered. The magnetic moment of the dipole is parallel to the free-stream velocity. The flow parameters correspond to a velocity of 7000 m/s at an altitude of approximately 65 km in the Earth’s atmosphere. The system of MHD equations (the Euler equations with volume MHD momentumand energy sources and the magnetic induction equation) was solved using the stabilization method. The calculations were carried out for two magnetic Reynolds numbers: (Re_m)₁ = 0.18 (corresponds to the parameters of the equilibrium ionized plasma in the shock layer) and (Re_m)₂ = 1.8 (the plasma conductivity increases by a factor of 10). The solutions obtained are analyzed, the effect of Re_m on the flow characteristics, namely, the shock wave stand-off from the body, the configuration of the vortex structures, and the aerodynamic and ponderomotive components of the body drag, is determined.     

Analytical solution of a problem of a collision of two hypersonic gas flows from symmetric sources

An asymptotic solution of the Euler equations that describe stationary interaction of two hypersonic gas flows from two identical spherically symmetric sources and an integral equation determining the shock wave shape are obtained with the use of a modified method of expansion of the sought functions with respect to a small parameter, which is the ratio of gas densities in the incoming flow and behind the shock wave. The solution of this equation near the axis of symmetry allows the shock wave stand-off distance from the contact plane and the radius of its curvature to be found. It is shown that the solution obtained agrees well with the known numerical solutions.     

Magnetohydrodynamic interaction in hypersonic air flow past a blunt body

Hypersonic MHD air flow past a blunt body in the presence of an external magnetic field is considered. The MHD effect on the flow consists in a significant increase in the shock wave stand-off from the body surface and a significant reduction in the heat flux to the wall (up to 50%). It is shown that even in the presence of a strong Hall effect the intensity of the magnetohydrodynamic interaction in the plasma behind the shock wave remains at a high level commensurable with the ideal case of the absence of a Hall effect.     

Validation of hypersonic chemical equilibrium flow calculations using ballistic-range data

The hypersonic flow field over a sphere flying in a ballistic-range is numerically simulated for the purpose of validating a hypersonic chemical equilibrium flow solver. The numerical results obtained are compared with available experimental data on the stand-off distance and the shape of the detached bow shock wave. In the calculation, an adaptive mesh is employed for a crisp capturing of the shock wave. Comparison with the experimental data reveals that the equilibrium flow solver can yield a fairly accurate prediction of the flow field. Received 18 November 1997 / Accepted 10 November 1998     

Hypersonic Flow Past the Spherical Nose of a Body in the Presence of a Magnetic Field

The hypersonic flow past the nose of a spherical body containing current sources generating a magnetic field is investigated theoretically and numerically. The magnetohydrodynamic (MHD) flow is analyzed on the basis of the complete system of Navier-Stokes equations containing the force and thermal MHD terms and the electrodynamic equations. Local and integral thermal and aerodynamic characteristics of the body are found. It is shown that the presence of a magnetic field makes it possible to reduce the heat flow to the body in the neighborhood of the stagnation point by several times. However, in this case the total body drag increases.     

Magnetohydrodynamic control of supersonic flow past bodies: Possibilities and undesirable effects

Basic problems of super-and hypersonic magnetohydrodynamics (MHD) associated with the determination of the integral characteristics of bodies and vehicles inside which there are systems generating a uniform magnetic field are considered. Three classes of flows, namely, flow in a hypersonic multimode fixed-geometry air-intake; internal and external flow in a model of a hypersonic vehicle containing an air-intake with an MHD generator, a combustion chamber, and a supersonic nozzle; and hypersonic flow past a blunt cone are studied using numerical simulation and theoretical analysis (on the basis of the complete averaged system of Navier-Stokes equations and the electrodynamic equations). Attention is concentrated on the presence of an additionalmagnetic force acting on the system generating themagnetic field and, consequently, on the body and initiating an additional drag (in the case of a vehicle-reducing its thrust). Attractive possibilities for MHD flow control, namely, an increase in the degree of flow compression in the air-intake, a reduction in the ignition length in the combustion chamber, and a decrease in the heat flux to the nose of the body, are noted, as well as negative effects associated with the action of the magnetic force on the bodies considered.     

热喷干扰气体模型对飞行器气动特性影响分析

针对不同气体模型对高超声速飞行器喷流反作用控制系统(RCS)热喷干扰流场模拟的计算效率和准确性问题, 基于喷流燃气物理化学模型, 通过数值求解含化学反应源项的三维N-S方程, 建立了飞行器RCS热喷干扰流场数值模拟方法, 分别采用化学反应流、反应冻结流、二元异质流以及空气喷流四种气体模型开展了典型外形热喷干扰流场的数值模拟, 研究了不同气体模型对热喷干扰流场结构、飞行器气动力热特性的影响, 分析了不同马赫数、飞行高度下的变化规律. 研究表明: 化学反应流模型计算精度较高, 计算与风洞试验数据的吻合程度优于其他三种简化模型; 在本文的低空条件下, 采用简化模型进行热喷干扰流场数值模拟, 会低估分离区大小, 使飞行器气动力特性预测出现偏差, 同时也会低估表面热环境, 对防热系统设计不利, 随着马赫数增加, 简化模型对气动力热特性预估的误差进一步增大, 同时不同简化模型之间的差异也进一步增大; 飞行高度较高时, 模型之间的差异减小, 此时可采用简化模型进行计算以提高计算效率. 本文的研究结果可为飞行器热喷干扰流场数值模拟及喷流反作用控制系统设计提供参考.      

On the structure of MHD shock waves in a viscous non-ideal gas

The structure of one-dimensional magnetohydrodynamics (MHD) shock waves is studied using the Navier–Stokes equations for the non-ideal gas phase. The exact solutions are obtained for the flow variables (i.e. particle velocity, temperature, pressure and change-in-entropy) within the shock transition region. The equation of state for a non-ideal gas is considered as given by Landau and Lifshitz. The effects of the non-idealness parameter and coefficient of viscosity of the gas are analysed on the flow variables assuming the magnetic field having only constant axial component. The findings confirm that the thickness of MHD shock front increases with decreasing values of the non-idealness parameter.     

Dynamic interaction of a magnetized solid body with a rarefied plasma flow

Dependences of the drag and lift coefficients of a magnetized sphere in a hypersonic rarefied plasma flow on the angle between the plasma flow velocity and the self-magnetic field induction vector of the body are obtained in a wide range of the ratio of the magnetic pressure to the plasma flow pressure. It is shown that changing the orientation of the magnetic field vector of the body and the incoming flow velocity can be used to control the dynamic interaction in the plasma–body system, namely, to decelerate and accelerate the magnetized sphere in a rarefied hypersonic plasma flow.